Domain Name Servers (DNS) translate domain names such as google.com into Internet Protocol (IP) numerical addresses such as 64.233.161.147. DNS servers typically reside on a remote network. When a user of a client computer needs to retrieve content from a remote web server, the user types the domain name in a browser's address bar, and presses the enter key. The client computer sends a request to the DNS server to return an IP address associated with the domain name. The DNS server replies with the IP address. Using the IP address, the client computer generates a request for the content from the remote web server. The remote web server returns the content to the client computer. The IP address is temporarily cached by the browser so that when the same domain name is requested in the future, the IP address is already known by the browser, so the browser can make future requests without first having to consult with the DNS server to obtain the IP address.
If there is a problem with the network, the translation request to the DNS server will not succeed. Generally, the network status is not available to the client computer, so it is not possible to distinguish between a non-functional network, and a slow response from the DNS server on a functional network. In such cases, browsers typically wait for a period of time and send repeated DNS requests. If the waiting and repeated requests fail to elicit a response from the DNS server in a specified period of time, the browser concludes that something is wrong with the network, times out, and displays an error message.
Likewise, if the browser is using a cached IP address, and there is a problem with the network, the browser cannot distinguish between a non-functional network and a slow response from the remote web server. In such cases, the browser waits for a period of time to receive a response, before timing out and displaying an error message.